This invention relates to improved methods and apparatus for electronically displaying a stereo pair of images needed to form a three-dimensional image.
A viewer of a two-dimensional image perceives depth when the two-eyes of the viewer see slightly different images of a three-dimensional scene. The brain of the viewer transforms the different images viewed by the left eye and right eye into information relating to the depth of the image.
An electronic stereo pair signal can be represented by: a left eye signal, Lxy, where x and y are the xy-coordinates of the image pixels and L.sub.xy is the brightness signal at the pixel with coordinates x, y; and by a right eye signal, Rxy, where x and y are the xy-coordinates of the image pixels and Rxy is the brightness signal at the pixel with coordinates x, y. Lxy and Rxy thus represent the intensity, or energy per unit area, for the left and right eye signals at the coordinates x, y. At present there exist two primary techniques of presenting an electronic stereo pair signal to a viewer such that a three-dimensional image is perceived. The first technique relies upon temporal multiplexing while the second technique relies upon spatial multiplexing to form a stereoscopic image.
In the first technique the two signals, Lxy and Rxy, can be provided in a temporally alternating sequential manner to a TV monitor, CRT, liquid crystal display, or other image display device so that at any point in time only one image (represented by either Lxy or Rxy) is present and visible. Downstream of the image display device, the system includes elements for enabling the left eye of the viewer to see only the left eye image Lxy and for enabling the right eye of the viewer to see only the right eye image Rxy. This can be achieved by having the viewer wear shuttering eyeglasses that are linked to and synchronized with the image display device. In another temporal multiplexing scheme, the image display device can be overlain by a fast switching polarizing device which polarizes the left-eye image one way and the right-eye image orthogonally so that the observer can simply wear passive polarizing glasses with the axis of polarization of the left-eye glass orthogonal to that of the right eye.
These systems, however, require very high speed imaging devices that can iteratively present a left-eye image, then erase it completely, then present a right-eye image, and then erase it completely. Temporal multiplexing systems also require equally high speed and efficient shutters or alternating polarizing devices.
A second prior art technique spatially multiplexes two signals, Lxy and Rxy. To multiplex the signals, the Lxy and Rxy signals are first segmented into two vertical columns of pixels. Two Lxy columns are then laterally compressed into one vertical column and two Rxy laterally columns are compressed into another vertical column. The laterally compressed Lxy and Rxy columns are then spatially alternated in the image signal. This technique creates a single image in which every other vertical column is the average of two columns of Lxy and each of the intervening columns is the average of two Rxy columns. The formed image is a spatially multiplexed signal of Lxy and Rxy. The spatially multiplexed image signal is then fed into an image-producing device in front of which is an array of polarizing micro strips. The polarizing micro strips must be oriented so that each column of compressed Lxy signals is aligned with strips of polarizers oriented along a first polarizing axis, and so that each column of compressed Rxy signals is aligned with strips of polarizers having a polarizing axis orthogonal to the first polarizing axis. The stereo pair can be then viewed with a set of passive polarizing glasses.
In addition to having complicated schemes for aligning the image producing device with the polarizing micro strips, the spatially multiplexing system also suffer from a loss of resolution in the stereoscopic image formed. In particular, spatial multiplexing systems inherently suffer from poor resolution caused by the compression of two columns of image data into one column of image data.
Accordingly, it is an object of the invention to electronically display a stereo pair of images having higher spatial resolution and improved temporal clarity.
These and other objects will be apparent from the description that follows.